1. Field of the Invention
This invention relates to valves for controlling the flow of liquids, and more particularly to plumbing valves of the type which, once turned on, shut-off automatically following a predetermined time interval. More specifically, the invention is directed to improvements in that type of automatic shut-off or self-closing valve in which a dashpot is used to control the length of time that the valve remains "on" or "open" to permit the flow of a liquid, typically water, therethrough.
2. Description of the Prior Art
In the prior art, a valve of the type characterized by the present invention is generally operated by an axially-displaceable valve stem or plunger which is adapted to be depressed against the force of a spring to turn "on" or "open" the valve, thereby permitting the liquid, typically water, to flow therethrough. The valve inside the water faucet usually comprises an annular shoulder of an elastomeric material, such as rubber, neoprene and the like, on the valve stem. This valve normally is held in its "off" or "closed" position by a compression spring which biases the annular shoulder against a circular valve seat secured to the body of the faucet and through which the plunger projects. In most cases, the dashpot is located within the body of the faucet and submerged in water. A piston is mounted on the plunger or valve stem and when the stem is axially depressed further into the body of the faucet, the piston is moved nearer the bottom of the dashpot chamber. Means for permitting the water in the dashpot chamber to be readily by-passed about the piston to the other side thereof during depression of the stem are employed to increase the speed at which the valve stem may be depressed and to reduce the magnitude of the force required to depress the stem to a minimum value so as to allow it to be manually operated. When the pg,3 force applied to effect depression of the valve stem is removed, the by-passing means are rendered inoperative. A restricted orifice is employed to provide fluid communication between the two chambers formed within the dashpot chamber on either side of the piston, and as the spring-biased valve stem to which the piston is mounted is urged into the valve's closed position, the orifice meters the water from one side of the piston to the other within the dashpot chamber, thereby slowing the upward, valve closing movement of the spring-biased plunger. Thus, it may be readily observed that the rate of valve closure is primarily controlled by the size of the dashpot orifice.
Examples of such prior art devices such as fundamentally described hereinbefore are disclosed in, and exemplified by, U.S. Pat. Nos. 95,054 (Smith); 2,181,581 (Fraser); 2,710,736 (Miller); 2,991,795 (Fraser, et. al.); 3,065,948 (Nolan) and 3,342,448 (Parkison). All of these devices employ water as the non-elastic, dashpot liquid.
In such prior art devices, the dashpot has been a source of considerable trouble in the maintenance of this type of faucet. Because the dashpot is submerged in and employs water as the dashpot liquid, the restricted orifice of the dashpot is subject to becoming fouled by hard water deposits, scale, foreign material, debris, etc. which renders the time delaying function of the dashpot inoperative. Consequently, it has been necessary in the past to disassemble the faucet quite frequently to maintain dashpot operation. Due to the relative complexity of the dashpot mechanism, such disassembly required the employing of someone, such as qualified plumber, having the requisite plumbing tools and skills.
In an attempt to remedy this situation, some of the prior art devices, namely: U.S. Pat. Nos. 2,181,581 (Fraser); 2,710,736 (Miller); 2,991,795 (Fraser, et. al.) and 3,065,948 (Nolan) all utilizes a movable pin which periodically moved in and out of the restricted orifice or water metering passageway to clear it of the restricting material blocking the metering passageway. However, even the use of such a pin to create a so-called "self-cleaning orifice" was found to be inadequate to effect reliable operation of the dashpot because within a very short period of time the mineralization will clog the liquid metering combination of the pin-and-orifice and thereby render it inoperative in any event.
Other attempts at improving the reliability fo the restricted orifice include the use of a flexible rubber annulus such as used in U.S. Pat. No. 3,065,948 (Nolan) to provide a throttling effect for the flow of water through the aperture in the annulus. This type of throttle valve has the advantage in a faucet of this type in that scale accumulations upon it may be broken free by expanding and contracting the rubber annulus. In essence, the action is likened to the pulsating action of the deicing boots which were once used on aircraft wings. However, in order to produce such pulsations in the rubber annulus, external adjustment is required. Further, such a rubber annulus is subject to not only variations in water pressure which produces a variation in the size of the restricted orifice, but to wear as well.
Additionally, in spite of the aforementioned attempts to improve the operational reliability of the dashpot, nevertheless, such reliability was not achieved. If the solid particles in the water are not filtered out before reaching the dashpot chamber, the particles will be deposited within the dashpot chamber and either completely fill it, or at the very least, unduly limit the stroke of the dashpot piston. In either case, the time delay is either significantly shortened or becomes "zero".
However, even though many of the prior art devices employed, such as U.S. Pat. Nos. 2,181,581 (Fraser); 2,991,795 (Fraser, et. al.); and 3,065,948 (Nolan), a filter or screen by which to block the flow of foreign particles or debris into the dashpot chamber and dashpot orifice, the filter would become clogged and, thereafterwards virtually stop the flow of water into the dashpot, thereby rendering it non-operative.
In addition, the viscosity of water acts as a practical limit on the amount of time delay available in a dashpot device such as found in the aforementioned patents.
Utilizing a liquid for dashpot metering other than water in a water supply system obviously requires that the metering liquid be isolated from the water supply system simply because it may be non-potable or even toxic. Prior art devices which have recognized the usefulness and desirability of substituting a liquid other than water in the dashpot, thereby preventing clogging by mineralization, scale formation, foreign debris and the like, include U.S. Pat. Nos.: 793,698 (Walter) and 2,825,427 (Steibel) both of which suggested the use of oil, glycerin or other hydraulic fluid.
It should be noted at this time, however, that not all hydraulic liquids are suitable even if non-toxic and/or potable. The liquid selected for use as the dashpot liquid must also have, as a practical matter, a rather large heat capacity to preclude it from being converted into its gaseous phase when the dashpot mechanism is used with a hot water supply. Should this occur, the dashpot time-delay would be reduced and/or the fluid seals may be unable to adequately contain the metering fluid in its gaseous phase. However, a major and unacceptable problem, nevertheless, arose in the use of these prior art devices, in that, during reciprocation of the valve stem or plunger, the fluid seal between the dashpot housing or body and the plunger permitted a small amount of the hydraulic fluid to be lost during each reciprocation. Consequently, after so many cycles of operation, the hydraulic fluid had to be replaced or the dashpot would become inoperative.
Steibel recognized the problem of hydraulic fluid loss inherent in each cycle of reciprocation of the dashpot plunger or piston stem. Steibel attempted to solve the effects of such losses of dashpot liquid when using a liquid other than water by incorporating a reservoir therein. However, it was quickly found that the use of a reservoir by which to re-supply the liquid lost merely delayed the inevitable, and did not solve the problem. For example, in the case of the Steibel patent, the reciprocation of the piston stem 22 in and out of the dashpot liquid resulted in some loss of the dashpot liquid as the piston stem 22 exited the body 10 even though the seals 23 wiped the piston stem 22 as it exited.
Also, it should be noted that even though Steibel employed hydraulic fluid as the dashpot liquid, due to the other structural and operational characteristics of the Steibel device, Steibel required the use of a filter means for preventing clogging of the control bore (see Column 4, lines 56 and 57). The use of such filters, as previously discussed, is undesirable because it merely delays the inevitable clogging which it purports to prevent, and, thereby, makes the dashpot mechanism unreliable.
Further, in the device of Walter, the hydraulic fluid disposed on the plunger or valve stem was, upon actuation thereof, placed within the water passageway, thereby placing an amount of hydraulic fluid in the water and contaminating it.
Still further, when annular fluid seals are used about the valve stem or plunger to prevent the hydraulic fluid from leaking out therebetween, a frictional force is created so that when the stem is actuated, the magnitude of the actuation force must not only move the plunger, but it must also overcome the frictional forces of the various fluid seals surrounding the stem. Consequently, in practice, the actuation force required is so great that small children of kindergarten age are unable to manually actuate the plunger to turn the faucet on, thereby rendering this kind of device unsuitable for use by children.
The present invention as disclosed hereinafterwards was discovered during the search for a solution to this perplexing problem.